International Journal of Science and Technology (IJST)

Capillary–thermocapillary driven entirely detached growth of the In₀.₅Ga₀.₅Sb in Vertical Directional Solidification under terrestrial gravity: Experimental evidence and Gadkari Detached Stability Criterion (GDSC)

A controlled vertical directional solidification (VDS) technique was developed for the terrestrial growth of bulk In₀.₅Ga₀.₅Sb crystals under capillary-dominated and diffusion-controlled conditions. The use of a vacuum-sealed ampoule significantly suppressed buoyancy-driven convection, establishing a stable environment in which solute transport occurred primarily through thermodiffusion. Under these conditions, contactless (detached) growth was sustained by the combined action of antimony vapor pressure and surface-tension forces, producing a uniform increasing micro-gap of 95–250μm and a stable crystal–melt interface. The grown crystals exhibited high structural and electronic quality, including low dislocation densities (~10³ cm⁻²), enhanced hardness (3.7 GPa), strong (220) preferential orientation, and carrier mobility up to 2.5 × 10⁴ cm² V⁻¹ s⁻¹. A growth rate of 2.5 mm h⁻¹ was achieved, exceeding typical rates reported for gradient-freeze and reduced-gravity experiments. Dimensionless analyses confirmed diffusion–capillary control of transport and interface stability. A Growth-deviation (GD) number is introduced to quantify the transition from buoyancy-dominated to diffusion-controlled growth. The results demonstrate that the VDS configuration provides a reliable terrestrial platform for studying detached, convection-suppressed solidification and for producing high-quality In₀.₅Ga₀.₅Sb crystals.